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Academic Commons Search Resultsen-usPolymer-Particle Nanocomposites: Size and Dispersion Effectshttp://academiccommons.columbia.edu/catalog/ac:153349
Moll, Joseph Francishttp://hdl.handle.net/10022/AC:P:14945Mon, 15 Oct 2012 00:00:00 +0000Polymer-particle nanocomposites are used in industrial processes to enhance a broad range of material properties (e.g. mechanical, optical, electrical and gas permeability properties). This dissertation will focus on explanation and quantification of mechanical property improvements upon the addition of nanoparticles to polymeric materials. Nanoparticles, as enhancers of mechanical properties, are ubiquitous in synthetic and natural materials (e.g. automobile tires, packaging, bone), however, to date, there is no thorough understanding of the mechanism of their action. In this dissertation, silica (SiO2) nanoparticles, both bare and grafted with polystyrene (PS), are studied in polymeric matrices. Several variables of interest are considered, including particle dispersion state, particle size, length and density of grafted polymer chains, and volume fraction of SiO2. Polymer grafted nanoparticles behave akin to block copolymers, and this is critically leveraged to systematically vary nanoparticle dispersion and examine its role on the mechanical reinforcement in polymer based nanocomposites in the melt state. Rheology unequivocally shows that reinforcement is maximized by the formation of a transient, but long-lived, percolating polymer-particle network with the particles serving as the network junctions. The effects of dispersion and weight fraction of filler on nanocomposite mechanical properties are also studied in a bare particle system. Due to the interest in directional properties for many different materials, different means of inducing directional ordering of particle structures are also studied. Using a combination of electron microscopy and x-ray scattering, it is shown that shearing anisotropic NP assemblies (sheets or strings) causes them to orient, one in front of the other, into macroscopic two-dimensional structures along the flow direction. In contrast, no such flow-induced ordering occurs for well dispersed NPs or spherical NP aggregates! This work also addresses the interfacial, rigid polymer layer, or `bound layer' which has long been of interest in polymer nanocomposites and polymer thin films. The divergent properties of the `bound layer' as compared to the bulk material can have very important effects on properties, including mechanical properties. This is especially true in polymer nanocomposites, where at high weight fractions, `bound layer' polymer can easily make up 20% or more of total material! Here we quantify this layer of bound polymer as a function of particle size, polymer molecular weight and other variables, primarily using thermogravimetric analysis but also dynamic light scattering and differential scanning calorimetry. We find that as nanoparticles become smaller, the `bound layer' systematically decreases in thickness. This result is quite relevant to explanations of many polymer nanocomposite properties that depend on size, including mechanical and barrier properties. Many additional important and new results are reported herein. These include the importance of dispersion state in the resulting mechanical properties of polymer-particle nanocomposites, where a systematic study showed an optimal dispersion state of a connected particle network. An additional and unexpected finding in this system was the critical dependence of composite properties on grafted chain length of particles. As the grafted chain length is increased, the strain which leads to yielding in a steady shear experiment is increased in a linear relationship. At very high rates, this yielding process completely switches mechanisms, from yielding of the particle network to yielding of the entangled polymer network! A surprising correlation between the amount of bound polymer in solution and in the bulk was also found and is interpreted herein. Self-assembly was further explored in a range of different systems and it was found that grafted particles and there mimics have vast potential in the creation of a wide array of particle superstructures. In concert, these experiments provide a comprehensive picture of mechanical reinforcement in polymer-particle nanocomposites. Not only is the dispersion state of the particles crucial, but the presence of grafted chains is also so for proper reinforcement. Here many routes to ideal dispersion are detailed and the important role of grafted chains is also resolved.Chemistryjfm2137Chemistry, Earth and Environmental Engineering, Chemical EngineeringDissertationsDynamics of Melt-mediated Crystallization of Amorphous Silicon Filmshttp://academiccommons.columbia.edu/catalog/ac:149824
Hu, Qiongyinghttp://hdl.handle.net/10022/AC:P:14058Mon, 16 Jul 2012 00:00:00 +0000This thesis reports on the new experimental findings and the corresponding conclusions that were made regarding the pulsed-laser-induced melting-and-solidification behavior of a-Si films. In particular, it focuses on investigating the melt-mediated crystallization details that are associated with the a-Si films, which presumably do not contain preexisting microcrystal clusters (as for instance can be formed via high-dose ion-irradiation of Si wafers and PECVD deposition of a-Si films). Whereas the behavior of microcrystalline-cluster-containing a-Si films within the partial-melting regime was well characterized and accounted for [1], a more intrinsic, and, therefore, more fundamentally important situation involving microcrystalline-cluster-deficient a-Si films in the partial melting regime has yet to be definitively resolved. The present thesis addresses this unsatisfactory situation. The samples used in this work consisted of 50nm to 200nm dehydrogenated PECVD a-Si films (with or without additional ion irradiation of the films) on SiO2-coated glass and quartz substrate. Single-shot irradiation experiments using an excimer-laser-based system were conducted at various pulse durations (30ns-Gaussian-profile beam to 250ns beam obtained via an optical pulse duration extender) and at various energy densities. Extensive in situ transformation analysis was performed using both front-side and back-side transient reflectance measurements also microstructural characterization of the irradiated films was conducted using TEM and AFM. The experimental findings obtained in this investigation reveal that these a-Si films can melt and solidify in ways that are quite distinct, more varied, and highly complex compared to those encountered in microcrystalline-cluster-rich a-Si films. Specifically: (1) spatially dispersed and temporally stochastic nucleation of crystalline solids occurring relatively effectively at the moving liquid-amorphous interface, (2) very defective crystal growth that leads to the formation of fine-grained Si proceeding, at least initially after the nucleation, at a sufficiently rapidly moving crystal solidification front, and (3) the propensity for local preferential re-melting of the defective regions and grain boundaries (while the beam is still on) are some of the fundamental factors that can participate and affect how these films melt and solidify. We discuss, by providing an extensive and critical review of the relevant papers, how the present conclusions are fundamentally distinct from those that have been made by the previous investigators in the field. The implications of these findings on the conventional ELA (i.e., excimer-laser annealing) method as well as the possibility of developing partial-melting-regime-based ultra-high-throughput crystallization methods are also discussed.Chemistry, Materials scienceApplied Physics and Applied Mathematics, Chemistry, Earth and Environmental EngineeringDissertationsSpin Chemistry of Guest@Host Systems: H2@C60 and Nitroxide@Octa Acidhttp://academiccommons.columbia.edu/catalog/ac:145461
Chen, Judy Yih-Chinghttp://hdl.handle.net/10022/AC:P:12855Wed, 21 Mar 2012 00:00:00 +0000This thesis describes the nuclear and electronic spin chemistry of incarcerated guest molecules to form a guest@host complex in conjunction with the utility of nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy. The first chapter describes the background and motivation of our scientific pursuit. Chapters 2-4 describe the nuclear spin chemistry of the two allotropes of elemental hydrogen, para-H2 and ortho-H2, incarcerated in C60, open-C60 and C70 fullerenes to form endofullerene guest@host complex, symbolized as pH2@fullerene and oH2@fullerene, respectively. Chapter 2 presents experimental results of the temperature dependence of the equilibrium of the interconversion of oH2@fullerene and pH2@fullerene and the use of different paramagnetic spin catalysts for this interconversion. Chapters 3 and 4 presents the spin-lattice relaxation (T1) and the paramagnet- enhanced relaxation, relaxivity (Rx) of o1,2H2@fullerene (1,2H2 = 1H-NMR-active H2 and HD) as well as the introduction of a new system for magnetic exploration: H2O@fullerene. Chapter 5 describes the electron spin chemistry of a paramagnetic nitroxide molecule incarcerated inside a capsule (nitroxide@octa acid) and presents supramolecular effects on paramagnetic interaction between the nitroxide incarcerated inside the capsuleplex with the nitroxide in bulk aqueous media studied by electron paramagnetic resonance (EPR) spectroscopy.Chemistryjyc2119Chemistry, Earth and Environmental Engineering, Chemical EngineeringDissertationsSolid phase modular synthesis of polymacromer brushes and their isolation as molecular products by photocleavage from the substratehttp://academiccommons.columbia.edu/catalog/ac:130663
Dach, Benjamin Isaac; Li, Xia; Turro, Nicholas J.; Koberstein, Jeffrey T.http://hdl.handle.net/10022/AC:P:10127Fri, 01 Apr 2011 00:00:00 +0000We report a novel solid phase method for the sequential coupling of heterobifunctional macromonomers to form a new class of polymeric materials that we refer to as polymacromers. Starting from an azide functional substrate, α-azido, ώ-protected-alkyne macromonomers are added step-by step by thermally initiated click reactions. After each addition step, the terminal alkyne group is deprotected to allow addition of another macromonomer. The use of highly chemoselective click chemistry for the coupling reactions allows virtually any macromonomer to be employed, regardless of its chemical nature. The polymacromers may be left as polymer brushes on the substrate, or can be isolated as molecular products by photocleavage of an ortho-nitrobenzyloxycarbonyl (NBOC) linkage incorporated at the substrate interface. The method is illustrated by forming homopolymacromers by sequential coupling of poly(tert-butyl acrylate) macromonomers. The results of characterization of the polymacromer bushes by ellipsometry, contact angle analysis and x-ray photoelectron spectroscopy, and direct measurements of the molecular weights of isolated products by gel permeation chromatography demonstrate that polymacromers can be prepared with a coupling efficiency approaching 100%.Chemistry, Chemical engineeringbid2101, xl2192, njt3, jk1191Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesThe Mechanism of Addition of Diazo-alkanes to Cyclopropanoneshttp://academiccommons.columbia.edu/catalog/ac:128184
Turro, Nicholas J.; Gagosian, Robert B.http://hdl.handle.net/10022/AC:P:9411Tue, 03 Aug 2010 00:00:00 +0000The addition of diazo-alkanes to cyclopropanones yields cyclobutanones whose structures may be predicted on the basis of conformational regulation of the migrating carbon-carbon bond.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesFavorskii rearrangement of some α-Bromo-ketoneshttp://academiccommons.columbia.edu/catalog/ac:128187
Turro, Nicholas J.; Gagosian, Robert B.; Rappe, Christoffer; Knutsson, Leifhttp://hdl.handle.net/10022/AC:P:9412Tue, 03 Aug 2010 00:00:00 +0000The base-induced rearrangement of α-halogenoketones to give carboxylic acid derivatives (Favorskii rearrangements) occurs by at least two mechanisms. The stereochemistry, and structure of many Favorskii products can be explained in terms of a cyclopropanone intermediate. However, a "benzylic-like" rearrangement appears to operate when the substrate ketone bears no α'-hydrogen, when the α'-hydrogen is relatively non-acidic, or when steric or strain factors inhibit cyclopropanone formation. In addition, the formation of a dipolar intermediate which may precede (or follow) cyclopropanone formation is supported by theoretical considerations, loss of stereospecificity upon rearrangement in polar solvents, the formation of α-substitution products as a side reaction, and the trapping of a possible Favorskii intermediate "dehydrohalogenate" to form a common intermediate leading to the same product.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesEnergy Transfer Processeshttp://academiccommons.columbia.edu/catalog/ac:128175
Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9408Mon, 02 Aug 2010 00:00:00 +0000A discussion of the major mechanisms for electronic energy transfer for organic molecules is presented. Application of the techniques and ideas of electronic energy transfer to study the properties of polymers is given.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesEnergy Storage and Release: Direct and Sensitized Photoreactions of Dewar Benzene and Prismanehttp://academiccommons.columbia.edu/catalog/ac:128172
Turro, Nicholas J.; Ramamurthy, V.; Katz, Thomas J.http://hdl.handle.net/10022/AC:P:9407Mon, 02 Aug 2010 00:00:00 +0000Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesCycloaddition Reactions of Carbonyl Compounds Possessing High Energy Contenthttp://academiccommons.columbia.edu/catalog/ac:128181
Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9410Mon, 02 Aug 2010 00:00:00 +0000Detailed structure and kinetic analyses of the photocycloaddition of alkanones to (a) α,β-unsaturated nitriles and (b) enol ethers have been performed. The excited singlet states of alkanones were found to add stereospecifically and regiospecifically to 3-unsaturated nitriles. Alkanone triplets do not add to unsaturated nitriles but instead transfer triplet excitation (at the diffusion controlled rate) and thereby sensitize dimerization and cis-trans isomerization of the nitrile. Even when all the alkanone singlets are quenched by a ground state nitrile, oxetane formation is relatively inefficient. The possibility is put forward that singlet exciplex of alkanone and nitrile is formed directly, but then dissociates (undergoes internal conversion) about ten times faster than it collapses to oxetane. In contrast, both S1 and T1 of alkanones add to enol ethers and effect both oxetane formation and cis-trans isomerization. Evidence is produced in support of singlet and triplet biradicals as intermediates to oxetanes. The possibility of a precursor to the biradicals is considered. Alkanone fluorescence quenching, by ethylenes known to form oxetanes, is used as a probe of the stereoelectronjc requirements of the quenching process and to study excited state conformations.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesThermal and Photochemical Generation of Electronically Excited Organic Molecules: Tetramethyl-1,2-dioxetane and Naphthvalenehttp://academiccommons.columbia.edu/catalog/ac:128178
Turro, Nicholas J.; Lechtken, Peterhttp://hdl.handle.net/10022/AC:P:9409Mon, 02 Aug 2010 00:00:00 +0000In this paper some examples of reactions which yield electronically excited products are presented. In particular, the 1,2-dioxetanes are discussed. These molecules cleave cleanly into two carbonyl fragments when heated or irradiated. It will be shown that these simple, high energy, four atom arrays can efficiently generate electronically excited carbonyl fragments when they decompose. Surprisingly, tetramethyl-1,2-dioxetane (V) yields acetone triplet selectively upon thermolysis or photolysis. A study of the kinetics of thermal decomposition of V as a function of solvent, and the mechanistic implications of these observations will be discussed. Based on summation of available evidence, we propose that the thermolyses of 1,2-dioxetanes require specific vibrational motions which enhance spin—orbit coupling as the molecule fragments, and allow efficient decomposition into triplet states. In the photochemistry of V an exceptional 'anti-Stokes' sensitization is demonstrated, which suggests the possibility of efficient execution of 'blue light' photochemistry with 'red light', and a 'quantum chain' reaction. It is demonstrated that, at 77°K, naphthvalene undergoes efficient photochemical conversion to naphthalene triplets. Finally, the relationship of radiationless electronic relaxation and primary photochemical processes is discussed in the framework of our results.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesQuenching of Chemiexcited Acetone Phosphorescence by Aryl Alkyl Ketones: A Search for Electronic Effectshttp://academiccommons.columbia.edu/catalog/ac:128162
Mirbach, M. F.; Ramamurthy, V.; Mirbach, M. J.; Turro, Nicholas J.; Wagner, P. J.http://hdl.handle.net/10022/AC:P:9404Mon, 02 Aug 2010 00:00:00 +0000Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesAnti-Stokes Photosensitization Concept and Demonstration of a "Red Light" to "Blue Light" Transformationhttp://academiccommons.columbia.edu/catalog/ac:128168
Turro, Nicholas J.; Brewer, David; Farneth, William; Ramamurthy, V.http://hdl.handle.net/10022/AC:P:9406Mon, 02 Aug 2010 00:00:00 +0000Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesPhotochemistry and Photophysics of a Polycyclic Azoalkane: Solvent and Temperature Effectshttp://academiccommons.columbia.edu/catalog/ac:128165
Turro, Nicholas J.; Ramamurthy, V.http://hdl.handle.net/10022/AC:P:9405Mon, 02 Aug 2010 00:00:00 +0000Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesPhotochemistry of organic molecules in microscopic reactorshttp://academiccommons.columbia.edu/catalog/ac:128124
Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9396Fri, 30 Jul 2010 00:00:00 +0000The photochemistry of dibenzyl ketone and its derivatives has been employed to investigate the ability of zeolite molecular sieves to modify and to control the reaction channels available to organic molecules adsorbed on the internal and external zeolite surfaces. It is found that the observed photochemistry is very sensitive to the size/shape characteristics of the substrate ketones and of the pores and internal void space of the zeolites. Although unprecedented reactions of ketones have been found to be induced by absorption of the ketones on the zeolite surfaces, the reactions are consistent with expectations based on the topological structure of the zeolite surfaces and on the mechanism of ketone photolysis in homogeneous solution.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesMicelles, Magnets and Molecular Mechanisms: Application to Cage Effects and Isotope Separationhttp://academiccommons.columbia.edu/catalog/ac:128133
Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9399Fri, 30 Jul 2010 00:00:00 +0000This report reviews the general problem of cage reactions of radical pairs and diradicals. Based on Wigner's spin conservation rule and the expectation that only singlet radical pairs can undergo cage reactions, a natural consequence is the expectation that it should be possible to observe magnetic effects on the reactions of radical pairs. It is shown that two types of magnetic effects should be possible: (1) Effects due to the application of the magnetic field of a laboratory magnet during a reaction; (2) Effects due to the interactions of nuclear magnetic momemts and electron magnetic moments. The experimental consequences of these magnetic effects are separation of isotopes based on differing nuclear magnetic moments and variation of the extent of cage reaction by variation of an applied field or by variation of nuclear magnetic moments. Striking experimental examples of these magnetic effects are provided by the photolysis of ketones in micellar solution and by the thermolysis of endoperoxides.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesAdiabatic ring opening in tethered naphthalene and anthracene cycloadductshttp://academiccommons.columbia.edu/catalog/ac:128130
Sundaresan, Arun K.; Jockusch, Steffen; Li, Yongjun; Lancaster, Jeffrey R.; Banik, Steven; Zimmerman, Paul; Blackwell, James M.; Bristol, Robert; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9398Fri, 30 Jul 2010 00:00:00 +0000The cycloadducts of tethered naphthalene and anthracene derivatives undergo photochemical ring opening to an electronically excited product with adiabatic yields up to 90%.Chemistryas3615, sj67, yl2560, jrl2132, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesApplication of Laser Photolysis to the Study of Reactive Intermediateshttp://academiccommons.columbia.edu/catalog/ac:128136
Turro, Nicholas J.; Aikawa, Masayuki; Butcher, Jared A.http://hdl.handle.net/10022/AC:P:9400Fri, 30 Jul 2010 00:00:00 +0000Excimer laser flash photolysis in the study of diphenyl carbene (DPC) reveals the presence of at least three transient species produced by excitation of a precursor at 249 nm in isooctane solution at room temperature depending on the concentration of O2 present. In an aerated solution, a fast first-order decay assigned to 3DPC leads to the formation of an unassigned species which also decays by first order kinetics to produce the observed product Ph2CO. In degassed solution, the fast first-order decay of a species to produce 3DPC which decays by second-order kinetics to produce the dimeric products observed.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesA New Materials-based Pitch Division Techniquehttp://academiccommons.columbia.edu/catalog/ac:128127
Gu, Xinyu; Bates, Christopher; Cho, Younjin; Costner, Elizabeth; Marzuka, Fernando; Nagai, Tomoki; Ogata, Toshiyuki; Shi, Chuan; Sundaresan, Arun K.; Turro, Nicholas J.; Bristol, Robert; Zimmerman, Paul; Willson, C. Granthttp://hdl.handle.net/10022/AC:P:9397Fri, 30 Jul 2010 00:00:00 +0000Several techniques have been proposed to achieve higher resolution from 193 nm optical lithography [1]. Most of these techniques require the design of new exposure tools or implementation of costly extra process steps. A new pitch division technique is reported, which doubles the resolution of conventional lithography tools by simply adding one component to the photoresist formulation. This technique creates a resist system that involves a series of linked photochemical reactions (A→B→C) in which a photoacid generator (PAG) produces an intermediate species (B) that is a strong acid, which in turn undergoes a reaction that produces a neutral and inert compound (C) that is the final product. The intermediate acid concentration is low at lower doses, but it is largely consumed at higher doses. At moderate doses, the acid concentration reaches its maximum. This property could, in principle, be exploited to double the frequency of a grating on a mask. One formulation that provides this sort of resist response incorporates both a photoacid generator and a photobase generator. This system was studied by simulation and a test formulation was demonstrated to produce the expected resist response.Chemistryas3615, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesExchange Effects and CIDEPhttp://academiccommons.columbia.edu/catalog/ac:128118
Jenks, William S.; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9394Tue, 27 Jul 2010 00:00:00 +0000Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesGas-Phase Quenching of Excitations as a Probe of Dynamics in Porous Silicashttp://academiccommons.columbia.edu/catalog/ac:128121
Drake, J. M.; Levitz, P.; Klafter, J.; Turro, Nicholas J.; Nitsche, K. Stephen; Cassidy, Karen F.http://hdl.handle.net/10022/AC:P:9395Tue, 27 Jul 2010 00:00:00 +0000The quenching of an electronically excited adsorbed molecule by gas-phase quenchers within the pore network of several porous silicas has been studied. It is proposed that the early-time quenching rate should scale with the mean pore size, Rp, for gas pressures in the Knudsen regime. We have experimentally observed such scaling in what we believe is the first study of these quenching reactions in a homologous series of morphologically similar porous silicas.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesDirect energy transfer from excited organic adsorbates to intrinsic defect sites in silicalitehttp://academiccommons.columbia.edu/catalog/ac:128112
Leheny, A. R.; Turro, Nicholas J.; Drake, J. M.http://hdl.handle.net/10022/AC:P:9392Tue, 27 Jul 2010 00:00:00 +0000The decay of the excited singlet state of an aromatic molecule such as naphthalene adsorbed to the surface of silica is nonexponential. This nonexponential decay is shown to result from a multipolar interaction between the excited adsorbate and the intrinsic defects of silica. We present experimental evidence for direct energy transfer between the donor molecules, naphthalene and 2-methoxynaphthalene, and acceptor defects sites of a crystalline silica zeloite (silicalite). The principal condition for direct energy transfer, spectral overlap between the optical absorption of the defects and the fluorescence emission of the adsorbate is demonstrated for this system, and the nonexponential relaxation of the donor is shown to be described by a Forster-type stretched exponential. Based on the spectral overlap and energy transfer rate determined, the intrinsic defect density of silicalite is calculated to be 3±2×10 cm^-3.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesA TR ESR Study of the Quenching of Photoexcited Dioxouranium (VI) Salts by Stable Nitroxyl Free Radicalshttp://academiccommons.columbia.edu/catalog/ac:128109
Khudyakov, I. V.; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9391Tue, 27 Jul 2010 00:00:00 +0000TR ESR spectroscopy was applied to the study of the quenching of excited dioxouranium (VI) (uranyl) nitrate and sulfate by stable nitroxyl radicals of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) family. Photoexcitation of uranyl in solutions of alcohols of moderate viscosity (η = 3-10 cP) in the presence of TEMPO leads to CIDEP signals of TEMPO due to a radical triplet pair mechanism (RTPM). Polarized nitroxyls were also observed in solutions of polyelectrolyte sodium poly(styrenesulfonate), NaPSS, in the presence of the nitroxyl with a positively charged trimethylammonium group. Photolysis of uranyl salts in solutions of alcohols leads to the generation of free radicals of alcohols. No CIDEP of these radicals was observed, distinguishing U2 2+* from its organic analog, the triplet benzophenone. The probable reason for the lack of polarization in uranyl photoreduction reactions is the difficult access of free radicals to the U atom of the solvated radical UO2+ (V); this atom bears the unpaired electron. The role of polyelectrolytes in the enhancement of the quenching of excited states is discussed. Results are in agreement with the statement that photoexcited uranyl has a triplet multiplicity.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesLuminescence of ruthenium(II) polypyridyls: evidence for intercalative binding to Z-DNAhttp://academiccommons.columbia.edu/catalog/ac:128115
Friedman, Alan E.; Kumar, Challa V.; Turro, Nicholas J.; Barton, Jacqueline K.http://hdl.handle.net/10022/AC:P:9393Tue, 27 Jul 2010 00:00:00 +0000Photophysical studies have been undertaken to characterize the binding interactions of enantiomers of Ru(phen)3(2+), Ru(DIP)3(2+), and racemic Ru(bpy)2dppz2+ (where phen = 1,10-phenanthroline, DIP = 4,7-diphenylphenanthroline, and dppz = dipyridophenazine) with Z-form poly d(GC). Parallel enhancements in steady state luminescent intensity and a lengthening of luminescent lifetimes are seen for ruthenium enantiomers with Z-DNA as for B-DNA but with enantioselectivities reversed. Greater enhancements are seen for delta-isomers with the right-handed helix but for lambda-isomers with the left-handed helix. Ru(bpy)2dppz2+, an avid intercalator in B-DNA, displays no luminescence free in aqueous solution, but luminesces brightly bound to either B- or Z-poly d(GC). Stern-Volmer quenching studies also support the enantioselective preference in binding to B-DNA by delta-isomers and a reversal with binding to Z-DNA preferentially by the lambda-isomers. Steady state polarization studies indicate a rigid association of the complexes with both B- and Z-DNA on the time-scale of their emission and again with symmetrical enantioselectivities for the left and right-handed helices. Given the well characterized intercalative association of the complexes with B-DNA, the parallel results seen here with Z-DNA point strongly to a comparable intercalative association with the Z-form helix. That molecules may interact with Z-DNA through intercalation has not been demonstrated previously and now requires consideration in describing the range of interactions of small molecules and proteins with Z-DNA.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesPhotochemistry of ketones adsorbed on size/shape selective zeolites. A supramolecular approach to persistent carbon centered radicalshttp://academiccommons.columbia.edu/catalog/ac:128100
Turro, Nicholas J.; McDermott, Ann E.; Lei, Xuegong; Li, Wei; Abrams, Lloyd; Ottavianai, M. Francesca; Beard, Hege Støgård; Houk, Kendall N.; Beno, Brett R.; Lee, Patrick S.http://hdl.handle.net/10022/AC:P:9388Mon, 26 Jul 2010 00:00:00 +00002H NMR, EPR, computational and product analyses of the photolysis of 2,4-diphenylpentan-3-one (DPP) adsorbed on MFI size/shape selective zeolites are consistent with supramolecular structural changes as a function of surface coverage that provide a novel method for the generation of persistent diffusing organic free radicals.Chemistrynjt3, aem5, xl9Chemistry, Earth and Environmental Engineering, Chemical Engineering, Biological SciencesArticlesPhotochemistry and magnetic resonance spectroscopy as probes of supramolecular structures and migration pathways of organic molecules and radicals adsorbed on zeoliteshttp://academiccommons.columbia.edu/catalog/ac:128097
Turro, Nicholas J.; Lei, Xuegong; Li, Wei; McDermott, Ann E.; Abrams, Lloyd; Ottavianai, M. Francesca; Beard, Hege Støgårdhttp://hdl.handle.net/10022/AC:P:9387Mon, 26 Jul 2010 00:00:00 +0000Magnetic resonance, surface area measurements and computational techniques have been integrated to elucidate the supramolecular photochemistry of two isomeric ketones adsorbed on two MFI zeolites (silicalite and ZSM-5) and to demonstrate that common factors proportional to the available external surface area operate to determine the measured parameters in each case.Chemistrynjt3, xl9, aem5Chemistry, Earth and Environmental Engineering, Chemical Engineering, Biological SciencesArticlesFrom Molecular Photochemistry to Supramolecular Photochemistry: A Paradigm for the 1990shttp://academiccommons.columbia.edu/catalog/ac:128103
Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9389Mon, 26 Jul 2010 00:00:00 +0000The paradigm of molecules and the covalent bond between atoms has been a powerful and unifying principle for chemistry and photochemistry for decades. We now consider a "paradigm shift" which has been occurring during the past two decades and which may take its place along side the molecular paradigm during the 1990s, namely, the paradigm of supramolecular chemistry.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesA Novel Well-Defined Linear Poly(methacrylic acid) Macromonomers for Biomaterial Applications: The Synthesis and Characterizationhttp://academiccommons.columbia.edu/catalog/ac:128028
Vojtova, Lucy; Turro, Nicholas J.; Koberstein, Jeffrey T.http://hdl.handle.net/10022/AC:P:9366Fri, 23 Jul 2010 00:00:00 +0000Chemistrynjt3, jk1191Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesFrom molecular chemistry to supramolecular chemistry to superdupermolecular chemistry. Controlling covalent bond formation through non-covalent and magnetic interactionshttp://academiccommons.columbia.edu/catalog/ac:128025
Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9365Fri, 23 Jul 2010 00:00:00 +0000The reactions of carbon centered radical pairs often involve diffusion controlled combination and/or disproportionation reactions which are non-selective. A triplet geminate pair of radicals is produced by the photolysis of suitable ketones. The reactions of such geminate pairs can be controlled though the application of supramolecular concepts which emphasize non-covalent interaction to steer the geminate pair toward a selected pathway. In addition, "superdupermolecular" concepts, which emphasize the control of radical pair reactions through the orientation of electron spins, can be employed to further control the course of geminate pair reactions. Examples of control of a range of the selectivity of geminate radical combinations, which form strong covalent bonds, through supramolecular and superdupermolecular effects will be presented for the photolysis of ketones adsorbed in the supercages of zeolites.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesMolecular mobility in polymer thin filmshttp://academiccommons.columbia.edu/catalog/ac:128046
Tseng, K. C.; Turro, Nicholas J.; Durning, Christopher Jameshttp://hdl.handle.net/10022/AC:P:9371Fri, 23 Jul 2010 00:00:00 +0000Fluorescence recovery after photobleaching was used to measure in-plane dye-probe diffusion coefficients, D, in thin films of monodisperse polystyrene supported on fused quartz substrates. The substrates were prepared with a high density of surface hydroxyl groups which interact favorably with repeat units of the polymer. The effects of temperature and film thickness were investigated, at temperatures above the bulk glass transition of the polymer, T_g, and in the range of film thicknesses from 1-10² times the radius of gyration (R_g) of individual polymer molecules. As the film thickness decreases towards R_g the value of D increases above the bulk values, with significant effects first appearing in films ≃20R_g. In the thinnest films studied, about 4R_g, the values of D lie as much as two orders over bulk values. At the same time, the temperature dependence of D becomes much weaker than in bulk. Analysis by free volume theory indicates that apparent values of both T_g and the thermal expansion coefficient for liquid state, α_L, decrease as the film thickness decreases. The possible effects of surface segregation of the dye probe are discussed.Chemistrynjt3, cjd2Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesFirst photosensitized enantiodifferentiating isomerization by optically active sensitizer immobilized in zeolite supercageshttp://academiccommons.columbia.edu/catalog/ac:128037
Wada, Takehiko; Shikimi, Masayuki; Inoue, Yoshihisa; Lem, George; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9369Fri, 23 Jul 2010 00:00:00 +0000Enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by (R)- or (S)-1-methylheptyl benzoate immobilized in zeolite supercages afforded the respective enantiomer pair, (—)- and (+)-(E)-isomer (1E) in 5% enantiomeric excess, whilst racemic 1E was obtained upon homogeneous-phase photosensitization with the same antipodal sensitizer pair, thus demonstrating for the first time that chirally modified zeolites not only serve as supramolecular photosensitizing media but also enhance the original enantiodifferentiating ability of chiral photosensitizer.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesRadical pair recombination stereoselectivity as a probe of magnetic isotope and magnetic field effectshttp://academiccommons.columbia.edu/catalog/ac:128053
Lem, George; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9372Fri, 23 Jul 2010 00:00:00 +0000Photolysis of meso- or dl-2,4-diphenylpentan-3-one within NaY zeolites, coadsorbed with a chiral inductor, lead to enantioselective radical pair recombinations which are sensitive to 13C isotope effects, but insensitive towards external magnetic field effects.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesPolyurethane Nanocompositeshttp://academiccommons.columbia.edu/catalog/ac:128031
Khudyakov, Igor V.; Zopf, R. David; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9367Fri, 23 Jul 2010 00:00:00 +0000This review describes the present state of science and technology of photopolymerizable (UV-curable) polyurethane (PU) nanocomposites which include nanosilica and organically-modified clay (organoclay). A number of documented improvements of properties of PU nanocomposites compared to the pristine PU are presented. Many data on the structure and properties of PU nanocomposites were obtained not only for UV-cured urethane acrylate oligomers, but also for nanocomposites produced in the dark reactions. These data are critically reviewed. There is an expectation in the field of dramatic improvement of properties of PU nanocomposites under low loading (1-5 wt%) of organoclay.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesA comparative time-resolved CW EPR and FT EPR investigation of the addition of 2-hydroxy-2-propyl radicals to acrylate and methacrylate monomershttp://academiccommons.columbia.edu/catalog/ac:128019
Weber, Matthias; Turro, Nicholas J.; Beckert, Dieterhttp://hdl.handle.net/10022/AC:P:9363Fri, 23 Jul 2010 00:00:00 +0000The addition of 2-hydroxy-2-propyl radicals to n-butyl acrylate and n-butyl methacrylate has been investigated by time-resolved continuous wave electron paramagnetic resonance (TR CW EPR) and time-resolved Fourier transform electron paramagnetic resonance (TR FT EPR). The 2-hydroxy-2-propyl radicals were generated by the photolysis of acetone in propan-2-ol (through hydrogen abstraction) and by the photolysis of a ketone 5(through Î±-cleavage). The TR CW and TR FT spectra were experimentally equivalent for the addition of 2-hydroxy-2-propyl radicals to n-butyl acrylate to produce 3a. However, there are distinct differences between the TR CW and TR FT spectra for the addition of 2-hydroxy-2-propyl radicals to n-butyl methacrylate which produces the radical adduct 4a. In particular, a number of hyperfine lines clearly present in the TR CW spectra are much weaker in, or are absent from, the TR FT spectra. The differences in the TR CW and TR FT spectra are attributed to hindered rotation, which is important in the spectrum of the adduct of 2-hydroxy-2-propyl radicals to n-butyl methacrylate (4a), but not in the spectrum of the adduct of 2-hydroxy-2-propyl radicals to n-butyl acrylate (3a). The hindered rotation is shown to selectively shorten the spinâ€“spin relaxation time, T2, for certain hyperfine lines in the spectrum of 4a, resulting in broadening or disappearance of these lines and explaining the differences between the TR CW and TR FT spectra.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesMagnetic and spin effects in the photoinitiation of polymerizationhttp://academiccommons.columbia.edu/catalog/ac:128034
Khudyakov, Igor V.; Arsu, Nergis; Jockusch, Steffen; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9368Fri, 23 Jul 2010 00:00:00 +0000Application of a moderate external magnetic field increases the efficiency of triplet photoinitiators of polymerization. The reasons for this observation are briefly outlined. Such well-documented magnetic and spin effects as the magnetic isotope effect (MIE) and chemically induced dynamic nuclear and electron polarization (CIDNP and CIDEP) have been observed under the photolysis of photoinitiators. CIDEP results are emphasized. The study of CIDEP under the photolysis of initiators allows the detection and identification of free radicals of initiators and the spin multiplicity of the reacting photoinitiator (triplet or singlet). The transfer of the spin polarization of the initiator free radical to monomers is a promising technique for following radical reaction pathways. The results of a CIDEP study of the sensitized decomposition of phosphine oxide photoinitiators are presented.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesRuthenium(II)—tris-bipyridine/titanium dioxide codoped zeolite Y photocatalysts: II. Photocatalyzed degradation of the model pollutant 2,4-xylidine, evidence for percolation behaviorhttp://academiccommons.columbia.edu/catalog/ac:128016
Bossmann, Stefan H.; Jockusch, Steffen; Schwarz, Peter; Baumeister, Bodo; Göb, Sabine; Schnabel, Claudia; Payawan, Leon; Pokhrel, Megh Raj; Wörner, Michael; Braun, André M.; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9362Fri, 23 Jul 2010 00:00:00 +0000A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy)3]2+ and TiO2 codoped zeolites Y is presented here. The [Ru(bpy)3]2+ and TiO2 codoped zeolites Y served as photocatalysts in the oxidation of the model compounds 2,4-dimethylaniline (2,4-xylidine) by H2O2 in an acidic aqueous medium. Zeolite-embedded TiO2(nano)particles play an important role in the degradation mechanism. The first step in this complex mechanism is the photoelectron transfer from photoexcited [Ru(bpy)3]2+*, located inside the supercage of zeolite Y, to a neighboring TiO2 nanoparticle. During this electron transfer process, electron injection into the conduction band of TiO2 is achieved. The second decisive step is the reaction of this electron with H2O2, which was previously chemisorbed at the surface-region of the TiO2 nanoparticles. In this reaction, a TiO2 bound hydroxyl radical (TiO2—HO ) is created. This highly reactive intermediate initiates then the oxidation of 2,4-xylidine, which enters the zeolites framework in its protonated form (Hxyl+). The formation of 2,4-dimethylphenol as first detectable reaction product indicated that this oxidation proceeds via an electron transfer mechanism. Furthermore, [Ru(bpy)3]3+, which was created in the initiating photoelectron transfer reaction between [Ru(bpy)3]2+* and TiO2, also takes place in the oxidation of Hxyl+. [Ru(bpy)3]2+ is recycled in that reaction, which also belongs to the group of electron transfer reactions. In addition to the primary steps of this particular Advanced Oxidation Process (AOP), the dependence of the efficiency of the 2,4-xylidine degradation as a function of the [Ru(bpy)3]2+ and TiO2 loadings of the zeolite Y framework is also reported here. The quenching of [Ru(bpy)3]2+* by H2O2 as well as the photocatalytic activity of the [Ru(bpy)3]2+ and TiO2 codoped zeolite Y catalysts both follow a distinct percolation behavior in dependence of their TiO2 content.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesIn situ EPR investigation of the addition of persistent benzyl radicals to acrylates on ZSM-5 zeolites. Direct spectroscopic detection of the initial steps in a supramolecular photopolymerizationhttp://academiccommons.columbia.edu/catalog/ac:128013
Lei, Xuegong; Jockusch, Steffen; Ottaviani, M. Francesca; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9361Fri, 23 Jul 2010 00:00:00 +0000Photolysis of dibenzyl ketone derivatives adsorbed on ZSM-5 zeolites produces persistent benzyl radicals (initiator radicals), which add to methyl acrylates (monomers) to generate persistent adduct radicals. Both initiator and adduct radicals are readily observable by conventional steady-state EPR spectroscopy at room temperature and are persistent for time periods ranging from seconds to many days. The rate of the formation and the amount of the adduct persistent radical formed depends on the structure of the initiator radical (benzyl radical derivative) and the structure of the monomer (acrylate derivative). The lifetimes of the initiator and adduct radicals depend on the supramolecular structure of the radical@zeolite complex and the diffusion and reaction dynamics of the radicals in the complex. The most intense signal and highest addition rate to methyl acrylate were observed for the smallest initiator radical, the benzyl radical, because of its high mobility and relatively rapid diffusion within the internal zeolite surface. With increasing length of an alkyl chain (methyl, ethyl, and pentyl) on either the initiator (Î± position of the radical) or monomer (alkyl group of acrylate ester), the rate of radical addition to the monomer decreased, a result that is consistent with the decreased mobility and diffusion of the initiator radical or monomer. Deuterium isotope experiments and variation of the methyl acrylate concentration demonstrated that the initial adduct radical from methyl acrylate adds to another methyl acrylate to generate a secondary adduct radical, which, in turn, can continue to propagate to form a polymer that is cross-linked to the zeolite crystals. The results demonstrate that EPR can be a powerful tool for the direct in situ analysis of supramolecular photochemistry involving radicals rendered persistent by supramolecular steric effects. The latter eliminate the need for sophisticated flash photolysis equipment to investigate the structure and dynamics of reactive radicals and require only the use of simpler steady-state lamps.Chemistryxl9, sj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesPhotoisomerization of 2,3-diphenylcyclopropane-1-carboxylic acid derivativeshttp://academiccommons.columbia.edu/catalog/ac:128010
Sivaguru, J.; Jockusch, Steffen; Turro, Nicholas J.; Ramamurthy, V.http://hdl.handle.net/10022/AC:P:9360Fri, 23 Jul 2010 00:00:00 +0000Contrary to what is known about cis-1,2-diphenylcyclopropane and its derivatives, we find that they have triplet energies of ca. 311 kJ molâ€“1, do not undergo intersystem crossing upon direct excitation, undergo the less common adiabatic photoisomerization to the corresponding trans isomers, and show emission from excited 1,3-diradical intermediates.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesOutlook for potential third-generation immersion fluidshttp://academiccommons.columbia.edu/catalog/ac:127985
López-Gejo, Juan; Kunjappu, Joy T.; Zhou, J.; Smith, Bruce W.; Zimmerman, Paul; Conley, Will; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9352Thu, 22 Jul 2010 00:00:00 +0000In a search for alkane candidates for 193 nm immersion fluids, several alkanes and cycloalkanes were synthesized, purified and screened to ascertain their absorption at 193 nm, refractive index and temperature dispersion coefficient in the context of the actual application. In general, cycloalkanes, and more specifically polycycloalkanes, possess a higher refractive index than do linear alkanes. Decalin, cyclodecane, perhydrophenanthreme (PHP), perhydrofluorene (PHF) and perhydropyrene (PHPY) are examined as potential second and third generation immersion fluids. The use of perhydropyrene, which possesses a high refractive index of 1.7014 at 193 nm, may be limited as an immersion fluid because of high absorption at 193 nm. Mixtures of cycloalkanes can lead to a higher enhancement of the refractive index together with a decrease on the viscosity. Exhaustive purification of the fluids is a critical step in determining the real absorption of the different fluids at 193 nm. Two simple purification processes of these cycloalkanes were developed that led to low absorption fluids in the VUV region. The possibility of forming the oxygen complex in aerated fluids was reduced by purging samples with argon or nitrogen. This easy elimination of the oxygen complex shows the weak bonding nature of this complex.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesAmplification of the Index of Refraction of Aqueous Immersion Fluids by Ionic Surfactantshttp://academiccommons.columbia.edu/catalog/ac:127988
Lee, Kwangjoo; Kunjappu, Joy T.; Jockusch, Steffen; Turro, Nicholas J.; Widerschpan, Tatjana; Zhou, Jianming; Smith, Bruce W.; Zimmerman, Paul; Conley, Willhttp://hdl.handle.net/10022/AC:P:9353Thu, 22 Jul 2010 00:00:00 +0000In order to find new immersion liquids to improve the resolution of 193 nm immersion photolithography, we have attempted to discover aqueous system possessing an index of refraction greater than that of water using aqueous surfactant systems. The index of refraction (RI) of both cationic and anionic surfactant systems were examined in the presence of wide range of inorganic salts, and parameters such as size of surfactants, concentrations, and temperature were varied. The refractive index (RI) was found to be increased in the presence of both anionic and cationic surfactants compared to those of water and also increased as a function of surfactant concentration. However the refractive index tends to increase much more strongly as a function of salt concentration. In our study, a maximum RI enhancement was observed from 6.5 M CdCl2 in 8.2 mM aqueous SDS solution. The effect of micellar properties such as the critical micelle concentration (cmc) and degree of ionization were systematically studied for aqueous SDS system in the presence of CdCl2. The correlation on index of refraction between empirical data and theoretical prediction were performed using the concept of molar refraction. Wavelength dependence of RI from theoretical prediction based on empirical equation was examined for various concentration of CdCl2 system and the results are reported in the paper.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesDevelopment and Evaluation of a 193nm Immersion Generation-Three Fluid Candidateshttp://academiccommons.columbia.edu/catalog/ac:127979
Zimmerman, Paul A.; Byers, Jeff; Rice, Bryan; Ober, Christopher K.; Giannelis, Emmanuel P.; Rodriguez, Robert; Wang, Dongyan; O'Connor, Naphtali; Lei, Xuegong; Turro, Nicholas J.; Liberman, Vladimir; Palmacci, Stephen; Rothschild, Mordechai; Lafferty, Neal; Smith, Bruce W.http://hdl.handle.net/10022/AC:P:9350Thu, 22 Jul 2010 00:00:00 +0000The need to extend 193nm immersion lithography necessitates the development of a third generation (Gen-3) of high refractive index (RI) fluids that will enable approximately 1.7 numerical aperture (NA) imaging. A multi-pronged approach was taken to develop these materials. One approach investigated the highest-index organic thus far discovered. The second approach used a very high refractive index nanoparticle to make a nanocomposite fluid. This report will describe the chemistry of the best Gen-3 fluid candidates and the systematic approach to their identification and synthesis. Images obtained with the Gen-3 fluid candidates will also be presented for a NA ≥ 1.7.Chemistryxl9, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesOptical Threshold Layer and Intermediate State Two-Photon PAG Approaches to Double Exposure Lithographyhttp://academiccommons.columbia.edu/catalog/ac:127976
Berro, Adam J.; Gu, Xinyu; O'Connor, Naphtali; Jockusch, Steffen; Nagai, Tomoki; Ogata, Toshiyuki; Zimmerman, Paul; Rice, Bryan J.; Adolph, Elizabeth; Byargeon, Travis; Gonzalez, Jose; Turro, Nicholas J.; Willson, C. Granthttp://hdl.handle.net/10022/AC:P:9349Thu, 22 Jul 2010 00:00:00 +0000Intermediate state two-photon (ISTP) photoacid generator (PAG) and optical threshold layer (OTL) approaches to double exposure lithography have been explored. We have synthesized "transparent" PAG and sensitizer compounds for use in ISTP systems and have demonstrated the possibility of utilizing such energy transfer systems to generate acid. We have also synthesized side chain liquid crystalline polymers and small molecule azobenzene compounds for use in OTL applications and have begun photoswitching studies.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesMethods for the synthesis and purification of polycycloalkane candidates for photolithography immersion fluids at 193 nm: requirements for removal of oxygenhttp://academiccommons.columbia.edu/catalog/ac:128007
López-Gejo, Juan; Kunjappu, Joy T.; Conley, Will; Zimmerman, Paul; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9359Thu, 22 Jul 2010 00:00:00 +0000Cycloalkanes are candidates for immersion fluids because of their potential for low absorption in the 193-nm region and for a high refractive index (RI). We have developed an empirical correlation between refractive index and density of alkanes, which allows a prediction of the best candidates for immersion fluids based on the alkane structure. In particular, the correlation reveals that polycycloalkanes such as perhydrophenanthrene (PHPh) and perhydrodropyrene (PHPy), which have a higher RI than linear or cyclic alkanes, will be excellent candidates for immersion fluids at 193 nm. Therefore, PHPh and PHPy were synthesized by exhaustive hydrogenation of phenanthrene and pyrene. However, methods for the purification of the synthesized and commercial alkanes such as cyclodecane (CYD), cyclohexane (CYX), pentane (PNT), and decalin (DEC) are required in order to determine the actual absorption of candidates at 193 nm. The presence of an absorbing impurity at 193 nm can cause the premature elimination of otherwise excellent potential candidates. A rather subtle impurity is molecular oxygen, which does not itself absorb at 193 nm, but which forms complexes with alkanes that do absorb at 193 nm. In this case, the "impurity" is readily eliminated by simple purging with nitrogen or argon gas.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticles157 nm Pellicles for Photolithography: Mechanistic Investigation of the Deep UV Photolysis of Fluorocarbonshttp://academiccommons.columbia.edu/catalog/ac:127991
Lee, Kwangjoo; Jockusch, Steffen; Turro, Nicholas J.; French, Roger H.; Wheland, Robert C.; Lemon, Michael F.; Braun, Andre M.; Widerschpan, Tatjana; Zimmerman, Paulhttp://hdl.handle.net/10022/AC:P:9354Thu, 22 Jul 2010 00:00:00 +0000The advance of 157 nm as the next photolithographic wavelength has created a need to for transparent and radiation durable polymers for the use as pellicles. The most promising materials for the pellicles are fluorinated polymers, but the currently available fluorinated polymers undergo photodegradation and/or photodarkening upon exposure to 157 nm irradiation. To understand the mechanism of the photodegradation and photodarkening of fluorinated polymers, mechanistic studies on the photolysis of liquid model fluorocarbons such as, perfluoro butylethyl ether and perfluoro-2H-3-oxa-heptane, were performed employing UV, NMR, FTIR, GC, and GC/MS analysis. All hydrogen containing compounds showed decreased photostability compared to the fully perfluorinated compounds. Irradiation in the presence of atmospheric oxygen showed reduced photodarkening compared to deoxygenated samples. Irradiations were performed at 157 nm, 172 nm, 185 nm, and 254 nm and showed only minor wavelength dependence. Mechanisms for photodegradation of the fluorocarbons were proposed, where Rydberg excited states are involved.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesStatus of High-Index Materials for Generation-Three 193nm Immersion Lithographyhttp://academiccommons.columbia.edu/catalog/ac:127997
Zimmerman, Paul A.; Peski, Chris van; Rice, Bryan; Byers, Jeff; Turro, Nicholas J.; Lei, Xuegong; López-Gejo, Juan; Liberman, Vladimir; Palmacci, Steve; Rothchild, Mordy; Whitker, Andrew; Blakey, Idriss; Chen, Lan; Dargaville, Bronwin; Liu, Hepinghttp://hdl.handle.net/10022/AC:P:9356Thu, 22 Jul 2010 00:00:00 +0000Generation-three (Gen-3) immersion lithography can be an enabler for the 32nm half-pitch node. For Gen-3 lithography to be successful, however, there must be three major breakthroughs in materials development: high refractive index ("high-index") lenses, high-index immersion fluids, and high-index photo-resists. Currently a material for a high-index lens element, lutetium aluminum garnet (LuAG), has been identified. However, suitable materials choices remain elusive for both the Gen-3 fluid and resist. This paper reviews the successes and failures in the search for Gen-3 high-index materials.Chemistrynjt3, xl9Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesDouble Exposure Materials: Simulation Study of Feasibilityhttp://academiccommons.columbia.edu/catalog/ac:128001
Byers, Jeffrey; Lee, Saul; Jen, Kane; Zimmerman, Paul; Turro, Nicholas J.; Willson, C. Granthttp://hdl.handle.net/10022/AC:P:9357Thu, 22 Jul 2010 00:00:00 +0000Double patterning and double exposure techniques have been proposed as possible methods for reducing half pitch resolution below k1=0.25. Both methods have the potential to reduce the theoretical lithographic half pitch to k1=0.125. Double patterning is a process-intensive method that requires multiple coat, develop, and etch steps to achieve the low k1 imaging. Double exposure processes have been proposed that do not require multiple coat, develop, or etch steps. Potentially, double exposure processes will have a lower cost of ownership that double patterning. However, double exposure materials have not yet been proven to work experimentally. Before applying significant effort to develop double exposure materials, their feasibility can be determined using rigorous simulation techniques. This work presents a feasibility study of four types of double exposure materials and their potential process windows.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesAn analysis of double exposure lithography optionshttp://academiccommons.columbia.edu/catalog/ac:127982
Lee, Saul; Byers, Jeffrey; Jen, Kane; Zimmerman, Paul; Rice, Bryan; Turro, Nicholas J.; Willson, C. Granthttp://hdl.handle.net/10022/AC:P:9351Thu, 22 Jul 2010 00:00:00 +0000The current optical photolithography technology is approaching the physical barrier to the minimum achievable feature size. To produce smaller devices, new resolution enhancement technologies must be developed. Double exposure lithography has shown promise as potential pathway that is attractive because it is much cheaper than double patterning lithography and it can be deployed on existing imaging tools. However, this technology is not possible without the development of new materials with nonlinear response to exposure dose. The performance of existing materials such as reversible contrast enhancement layers (rCELs) and theoretical materials such as intermediate state two-photon (ISTP) and optical threshold layer (OTL) materials in double exposure applications was investigated through computer simulation. All three materials yielded process windows in double exposure mode. OTL materials showed the largest process window (DOF 0.137 µm, EL 5.06 %). ISTP materials had the next largest process window (DOF 0.124 µm, EL 3.22 %) followed by the rCEL (0.105 µm, 0.58 %). This study is an analysis of the feasibility of using the materials in double exposure mode.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesAmplification of the index of refraction of aqueous immersion fluids with crown ethershttp://academiccommons.columbia.edu/catalog/ac:128004
López-Gejo, Juan; Kunjappu, Joy T.; Turro, Nicholas J.; Conley, Willhttp://hdl.handle.net/10022/AC:P:9358Thu, 22 Jul 2010 00:00:00 +0000There is a current need for high refractive index (RI) materials that can be used in aqueous systems for improving 193-nm immersion photolithography. Although heavy metal salts such as Ca2+ and Ba2+ have the potential to substantially increase the RI of aqueous solutions, the water solubility of these salts with common anions is often too low to achieve concentrations that significantly increase the RI to the desired values. We therefore investigate the use of crown ethers to enhance the solubility of these cations. Most of crown ethers are soluble in water, are inexpensive materials, and are available commercially. 15-crown-5-ether and 12-crown-4-ether are liquids at room temperature and therefore can be used as neat immersion fluids without dilution in water. Saturation of crown ethers with inorganic salts do not lead to any increase in the refractive index due to their low solubility in such an apolar medium. Thus, the use of inorganic salts as refractive index enhancement agents does not seem to be a desirable proposition in the present case. Instead, the use of crown ethers or their derivatives can be an alternative system, since these compounds have properties such as density, viscosity, and boiling point similar to aqueous media.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesDegradation of Hydrocarbon Fluids in the Immersion Lithography at 193 nmhttp://academiccommons.columbia.edu/catalog/ac:127994
O'Connor, Naphtali A.; Liberman, Vladimir; Lei, Xuegong; López-Gejo, Juan; Turro, Nicholas J.; Zimmerman, Paul A.http://hdl.handle.net/10022/AC:P:9355Thu, 22 Jul 2010 00:00:00 +0000The search for successful generation 3 immersion lithography fluids is focused on high refractive index fluids which are transparent to 193 nm light. This search has led to saturated hydrocarbons which have been shown potential in this field. This paper discusses our observations that many immersion fluid candidates (saturated hydrocarbons and acetonitrile) were observed to polymerize upon irradiation with 193 nm light.Chemistryxl9, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesMaterials modeling and development for use in double-exposure lithography applicationshttp://academiccommons.columbia.edu/catalog/ac:127969
Lee, Saul; Jen, Kane; Willson, C. Grant; Byers, Jeffrey; Zimmerman, Paul; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9347Tue, 20 Jul 2010 00:00:00 +0000The current optical photolithography technology is approaching the physical barrier to the minimum achievable feature size. To produce smaller devices, new resolution enhancement technologies must be developed. Double-exposure lithography has shown promise as a potential pathway that is attractive because it is much cheaper than double-patterning lithography and can be deployed on existing imaging tools. However, this technology is not possible without the development of new materials with nonlinear response to exposure dose. The performance of existing materials such as reversible contrast enhancement layers (rCELs), and theoretical materials such as intermediate state two-photon (ISTP) and optical threshold layer (OTL) materials in double-exposure applications have been investigated through computer simulation. All three materials yielded process windows in double-exposure mode. OTL materials showed the largest process window (depth of focus (DOF) 0.14 µm, exposure latitude (EL) 5.1%). ISTP materials had the next-largest process window (DOF 0.12 µm, EL 3.2%), followed by the rCEL (0.11 µm, 0.58%). This study is an analysis of the feasibility of using the materials in double-exposure mode.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesFundamental Study of Optical Threshold Layer Approach Towards Double Exposure Lithographyhttp://academiccommons.columbia.edu/catalog/ac:127973
Gu, Xinyu; Berro, Adam J.; Cho, Younjin; Jen, Kane; Lee, Saul; Nagai, Tomoki; Ogata, Toshiyuki; Durand, William J.; Sundaresan, Arun K.; Lancaster, Jeffrey R.; Jockusch, Steffen; Zimmerman, Paul; Turro, Nicholas J.; Willson, C. Granthttp://hdl.handle.net/10022/AC:P:9348Tue, 20 Jul 2010 00:00:00 +0000Intermediate state two-photon (ISTP) photoacid generator (PAG) and optical threshold layer (OTL) approaches to double exposure lithography have been explored. We have synthesized "transparent" PAG and sensitizer compounds for use in ISTP systems and have demonstrated the possibility of utilizing such energy transfer systems to generate acid. We have also synthesized side chain liquid crystalline polymers and small molecule azobenzene compounds for use in OTL applications and have begun photoswitching studies.Chemistryas3615, jrl2132, sj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesDesign and synthesis of a photocleavable biotinylated nucleotide for DNA analysis by mass spectrometryhttp://academiccommons.columbia.edu/catalog/ac:127798
Bai, Xiaopeng; Kim, Sobin; Li, Zengmin; Turro, Nicholas J.; Ju, Jingyuehttp://hdl.handle.net/10022/AC:P:9343Tue, 20 Jul 2010 00:00:00 +0000We report here the design, synthesis and evaluation of a novel photocleavable (PC) biotinylated nucleotide analog, dUTP-PC-Biotin, for DNA polymerase extension reaction to isolate DNA products for mass spectrometry (MS) analysis. This nucleotide analog has a biotin moiety attached to the 5-position of 2'-deoxyribouridine 5'-triphosphate via a photocleavable 2-nitrobenzyl linker. We have demonstrated that dUTP-PC-Biotin can be faithfully incorporated by the DNA polymerase Thermo Sequenase into the growing DNA strand in a DNA polymerase extension reaction and that its incorporation does not hinder the addition of the subsequent nucleotide. Therefore, the DNA extension fragments generated by using the dUTP-PC-Biotin can be efficiently isolated by a streptavidin-coated surface and recovered by near-UV light irradiation at room temperature in mild condition for further analysis without using any chemicals or heat. Single and multiple primer extension reactions were performed using the dUTP-PC-Biotin to generate DNA products for MALDI-TOF MS analysis. Such nucleotide analogs that carry a biotin and a photocleavable linker will allow the isolation and purification of DNA products under mild conditions for MS-based genetic analysis by DNA sequencing or multiplex single nucleotide polymorphism (SNP) detection. Furthermore, these nucleotide analogs should also be useful in isolating DNAâ€“protein complexes under non-denaturing conditions.Chemistry, Chemical engineeringzl79, njt3, dj222Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesInfluence of capping groups on the synthesis of γ-Fe2O3 nanocrystalshttp://academiccommons.columbia.edu/catalog/ac:127795
Yin, Ming; Willis, Amanda; Redl, Franz; Turro, Nicholas J.; O'Brien, Stephen P.http://hdl.handle.net/10022/AC:P:9342Tue, 20 Jul 2010 00:00:00 +0000Monodisperse and uniform γ-Fe_2O_3 (maghemite) nanocrystals of variable size were prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)_5] in the presence of surfactants, following controlled oxidation with trimethylamine N-oxide as a mild oxidant. The influence of carboxylic acids with variable alkyl carbon chain lengths on the synthesis of γ-Fe_2O_3 nanocrystals was investigated. The effect of the molar ratios of surfactant to iron precursor was also studied. The nanocrystals were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD showed the particles were highly crystalline at the nanometer scale. The results showed that the size and shape of the nanocrystal is strongly influenced by the decomposition temperature of iron pentacarbonyl and closely related to the length of carbon chain of the capping groups and the molar ratio of surfactant to iron precursor. Following controlled evaporation from nonpolar solvents, self-assembly into two-dimensional arrays could be observed by TEM. It was also found that the distance between the nanocrystals in self-assembled structures matched the length of the capping molecules very well.Chemistrynjt3Applied Physics and Applied Mathematics, Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesPyrene binary probes for unambiguous detection of mRNA using time-resolved fluorescence spectroscopyhttp://academiccommons.columbia.edu/catalog/ac:127801
Martí, Angel A.; Li, Xiaoxu; Jockusch, Steffen; Li, Zengmin; Raveendra, Bindu; Kalachikov, Sergey M.; Russo, James J.; Morozova, Irina; Puthanveettil, Sathyanarayanan V.; Ju, Jingyue; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9344Tue, 20 Jul 2010 00:00:00 +0000We report here the design, synthesis and application of pyrene binary oligonucleotide probes for selective detection of cellular mRNA. The detection strategy is based on the formation of a fluorescent excimer when two pyrene groups are brought into close proximity upon hybridization of the probes with the target mRNA. The pyrene excimer has a long fluorescence lifetime (>40 ns) compared with that of cellular extracts (∼7 ns), allowing selective detection of the excimer using time-resolved emission spectra (TRES). Optimized probes were used to target a specific region of sensorin mRNA yielding a strong excimer emission peak at 485 nm in the presence of the target and no excimer emission in the absence of the target in buffer solution. While direct fluorescence measurement of neuronal extracts showed a strong fluorescent background, obscuring the detection of the excimer signal, time-resolved emission measurements indicated that the emission decay of the cellular extracts is ∼8 times faster than that of the pyrene excimer probes. Thus, using TRES of the pyrene probes, we are able to selectively detect mRNA in the presence of cellular extracts, demonstrating the potential for application of pyrene excimer probes for imaging mRNAs in cellular environments that have background fluorescence.Chemistrylx2109, sj67, zl79, br2155, sk363, jjr4, im198, sp2068, dj222, njt3Chemistry, Earth and Environmental Engineering, Neuroscience, Chemical EngineeringArticlesOxygen pressure measurement using singlet oxygen emissionhttp://academiccommons.columbia.edu/catalog/ac:127804
Khalil, Gamal E.; Chang, Alvin; Gouterman, Martin; Callis, James B.; Dalton, Larry R.; Turro, Nicholas J.; Jockusch, Steffenhttp://hdl.handle.net/10022/AC:P:9345Tue, 20 Jul 2010 00:00:00 +0000Pressure sensitive paint (PSP) provides a visualization of two-dimensional pressure distributions on airfoil and model automobile surfaces. One type of PSP utilizes platinum tetra(pentafluorophenyl)porphine (PtTFPP) dissolved in a fluoro-polymer film. Since the intense 650 nm triplet emission of PtTFPP is quenched by ground state oxygen, it is possible to measure two-dimensional oxygen concentration from the 650 nm emission intensity using a Stern-Volmer-type relationship. This article reports an alternative luminescence method to measure oxygen concentration based on the porphyrin-sensitized 1270 nm singlet oxygen emission, which can be imaged with an InGaAs near infrared camera. This direct measurement of oxygen emission complements and further validates the oxygen measurement based on PtTFPP phosphorescence quenching. Initial success at obtaining a negative correlation between the 650nm PtTFPP emission and the 1270 nm O_2 emission in solution led us to additional two-dimensional film studies using surfaces coated with PtTFPP, MgTFPP, and H_2TFPP in polymers in a pressure and temperature controlled chamber.Chemistrynjt3, sj67Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesStereoselective E/Z photoisomerization of oxazolidinone functionalized enecarbamates: direct and triplet sensitized irradiationhttp://academiccommons.columbia.edu/catalog/ac:127792
Saito, Hideaki; Sivaguru, Jayaraman; Jockusch, Steffen; Inoue, Yoshihisa; Adam, Waldemar; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:9341Mon, 19 Jul 2010 00:00:00 +0000Oxazolidinone-functionalized enecarbamates undergo diastereoselective E/Z photoisomerization upon direct and triplet sensitized irradiations with chiral/achiral sensitizers, showing that the enhanced product diastereoselectivity depends on the solvent and temperature.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesDirect measurement of the singlet oxygen lifetime in zeolites by near-IR phosphorescencehttp://academiccommons.columbia.edu/catalog/ac:125443
Jockusch, Steffen; Sivaguru, J.; Turro, Nicholas J.; Ramamurthy, V.http://hdl.handle.net/10022/AC:P:8611Wed, 31 Mar 2010 00:00:00 +0000Time-resolved near-IR phosphorescence spectroscopy was employed to determine the lifetime of singlet oxygen in Y-zeolites and porous silica and it was found to depend strongly on the alumina content of the zeolite.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesCombinatorial fluorescence energy transfer molecular beacons for probing nucleic acid sequenceshttp://academiccommons.columbia.edu/catalog/ac:125440
Li, Xiaoxu; Li, Zengmin; Martí, Angel A.; Jockusch, Steffen; Stevens, Nathan; Akins, Daniel L.; Turro, Nicholas J.; Ju, Jingyuehttp://hdl.handle.net/10022/AC:P:8610Mon, 29 Mar 2010 00:00:00 +0000We report the design, synthesis, and characterization of molecular beacons (MB) consisting of three distinct fluorophores, 6-carboxyfluorescein (Fam), N,N,N ,N -tetramethyl-6-carboxyrhodamine (Tam), and Cyanine-5 (Cy5). The primary light absorber/energy donor (Fam) is located on one terminus of the MB, whereas the primary energy acceptor/secondary donor (Tam) and secondary acceptor (Cy5) are located at the other terminus of the MB. In the absence of target DNA or RNA, the MB exists in the stem-closed form. Excitation of Fam initiates an energy transfer cascade from Fam to Tam and further to Cy5 generating unique fluorescence signatures defined as the ratio of the emission from each of the three fluorophores. This energy transfer cascade was investigated in detail by steady-state and time-resolved fluorescence spectroscopy, as well as fluorescence depolarization studies. In the presence of the complementary target DNA, the MB opened efficiently and hybridized with the target separating Fam and Tam by a large distance, so that energy transfer from Fam to Tam was blocked in the stem-open form. This opening of the MB generates a "bar code" fluorescence signature, which is different from the signature of the stem-closed MB. The fluorescence signature of this combinatorial fluorescence energy transfer MB can be tuned by variation of the spacer length between the individual fluorophores.Chemistrylx2109, zl79, sj67, njt3, dj222Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesMolecular beacons with intrinsically fluorescent nucleotideshttp://academiccommons.columbia.edu/catalog/ac:125434
Martí, Angel A.; Jockusch, Steffen; Li, Zengmin; Ju, Jingyue; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8609Thu, 25 Mar 2010 00:00:00 +0000We report the design, synthesis and characterization of a novel molecular beacon (MB-FB) which uses the fluorescent bases (FB) 2-aminopurine (AP) and pyrrolo-dC (P-dC) as fluorophores. Because the quantum yield of these FB depend on hybridization with complementary target, the fluorescent properties of MB-FB were tuned by placing the FB site specifically within the MB such that hybridization with complementary sequence switches from single strand to double strand for AP and vice versa for P-dC. The MB-FB produces a ratiometric fluorescence increase (the fluorescence emission of P-dC over that of AP in the presence and absence of complementary sequence) of 8.5 when excited at 310 nm, the maximum absorption of AP. This ratiometric fluorescence is increased to 14 by further optimizing excitation (325 nm). The fluorescence lifetime is also affected by the addition of target, producing a change in the long-lived component from 6.5 to 8.7 ns (Exc. 310 nm, Em. 450 nm). Thermal denaturation profiles monitored at 450 nm (P-dC emission) show a cooperative denaturation of the MB-FB with a melting temperature of 53°C. The thermal denaturation profile of MB-FB hybridized with its target shows a marked fluorescence reduction at 53°C, consistent with a transition from double stranded helix to random coil DNA.Chemistry, Chemical engineeringsj67, zl79, dj222, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesSpectroscopic investigation of a FRET molecular beacon containing two fluorophores for probing DNA/RNA sequenceshttp://academiccommons.columbia.edu/catalog/ac:125431
Jockusch, Steffen; Martí, Angel A.; Turro, Nicholas J.; Li, Zengmin; Li, Xiaoxu; Ju, Jingyue; Stevens, Nathan; Akins, Daniel L.http://hdl.handle.net/10022/AC:P:8608Thu, 25 Mar 2010 00:00:00 +0000We report the design, synthesis, and characterization of a molecular beacon (MB) consisting of two fluorescent dyes (Alexa 488 and RedX) for DNA and RNA analysis. In the absence of the target DNA or RNA the MB is in its stem-closed form and shows efficient energy transfer from the donor (Alexa) to the acceptor (RedX), generating mostly fluorescence from RedX. In the presence of the complementary target DNA the MB opened efficiently, hybridizes with the target DNA, and energy transfer is blocked in the stem-open form. This attachment to the target generates a fluorescence signature, which is clearly distinguishable from the fluorescence signature of the stem-closed form, allowing for ratiometric analysis of the fluorescence signal. In addition to steady-state fluorescence analysis, time resolved fluorescence (ps time range) and fluorescence depolarization studies were performed. We show that fluorescence lifetime and fluorescence depolarization measurements are useful analytical tools to optimize the MB design.Chemistrysj67, njt3, zl79, lx2109Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesCoupled translation-rotation eigenstates of H2 in C60 and C70 on the spectroscopically optimized interaction potential: Effects of cage anisotropy on the energy level structure and assignmentshttp://academiccommons.columbia.edu/catalog/ac:125410
Xu, Minzhong; Sebastianelli, Francesco; Gibbons, Brittney R.; Bačić, Zlatko; Lawler, Ronald; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8603Wed, 24 Mar 2010 00:00:00 +0000We have developed a quantitatively accurate pairwise additive five-dimensional (5D) potential energy surface (PES) for H2 in C60 through fitting to the recently published infrared (IR) spectroscopic measurements of this system for H2 in the vibrationally excited ν = 1 state. The PES is based on the three-site H2-C pair potential introduced in this work, which in addition to the usual Lennard-Jones (LJ) interaction sites on each H atom of H2 has the third LJ interaction site located at the midpoint of the H-H bond. For the optimal values of the three adjustable parameters of the potential model, the fully coupled quantum 5D calculations on this additive PES reproduce the six translation-rotation (T-R) energy levels observed so far in the IR spectra of H2@C60 to within 0.6%. This is due in large part to the greatly improved description of the angular anisotropy of the H2-fullerene interaction afforded by the three-site H2-C pair potential. The same H2-C pair potential spectroscopically optimized for H2@C60 was also used to construct the pairwise additive 5D PES of H2 (v = 1) in C70. This PES, because of the lower symmetry of C70 (D5h) relative to that of C60 (Ih), exhibits pronounced anisotropy with respect to the direction of the translational motion of H2 away from the cage center, unlike that of H2 in C60. As a result, the T-R energy level structure of H2 in C70 from the quantum 5D calculations on the optimized PES, the quantum numbers required for its assignment, and the degeneracy patterns which arise from the T-R coupling for translationally excited H2 are all qualitatively different from those determined previously for H2@C60 [M. Xu et al., J. Chem. Phys. 128, 011101 (2008)].Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesQuantum dynamics of coupled translational and rotational motions of H2 inside C60http://academiccommons.columbia.edu/catalog/ac:125413
Xu, Minzhong; Sebastianelli, Francesco; Gibbons, Brittney R.; Bačić, Zlatko; Lawler, Ronald; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8604Wed, 24 Mar 2010 00:00:00 +0000We report rigorous quantum calculations of the translation-rotation (T-R) eigenstates of the H_2 molecule in C60. The resulting level structure can be explained in terms of a few dominant features. These include the coupling between the orbital and the rotational angular momenta of H_2 to give the total angular momentum λ, and the splitting of the sevenfold degeneracy of T-R levels with λ = 3 by the nonsphericity of C60, according to the rules of the icosahedral I_h group.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesVibrational deactivation of singlet oxygen: does it play a role in stereoselectivity during photooxygenation?http://academiccommons.columbia.edu/catalog/ac:125395
Solomon, Marissa Rowanda; Sivaguru, J.; Jockusch, Steffen; Adam, Waldemar; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8598Wed, 24 Mar 2010 00:00:00 +0000Oxazolidinone-substituted enecarbamates offer a system to explore vibrational quenching and the strategic placement of CH bonds as a method for manipulating the stereoselectivity of photoreactions.Chemistryms2201, sj67, njt3Chemistry, Earth and Environmental Engineering, Chemical Engineering, Biomedical EngineeringArticlesChlorophyll derivatives as visual pigments for super vision in the redhttp://academiccommons.columbia.edu/catalog/ac:125404
Washington, Ilyas; Zhou, Jilin; Jockusch, Steffen; Turro, Nicholas J.; Nakanishi, Koji; Sparrow, Janet R.http://hdl.handle.net/10022/AC:P:8601Wed, 24 Mar 2010 00:00:00 +0000The primary event in vision is light-initiated activation of visual pigments. All visual pigments consist of the protein opsin bound to 11-cis-retinal and are responsible for initiating the transformation of light into an electrical signal. In a mouse model, we show that derivatives of chlorophyll can act as visual pigments initiating the transformation of light into an electrical signal and thus change the primary event in vision to initial activation of a chlorophyll derivative. Electroretinographic b-wave amplitudes recorded in response to red and blue light were two-fold greater in mice administered chlorin e6, which accumulated in photoreceptor outer segments.Chemistryiw2101, jz219, sj67, njt3, kn5, jrs88Chemistry, Earth and Environmental Engineering, Chemical Engineering, Ophthalmology, Pathology and Cell BiologyArticlesControlled diastereoselectivity at the alkene-geometry through selective encapsulation: E-Z photoisomerization of oxazolidinone-functionalized enecarbamates within hydrophobic nano-cavitieshttp://academiccommons.columbia.edu/catalog/ac:125401
Saito, Hideaki; Sivaguru, J.; Jockusch, Steffen; Dyer, Joanne; Inoue, Yoshihisa; Adam, Waldemar; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8600Wed, 24 Mar 2010 00:00:00 +0000Photoisomerization of encapsulated Z-enecarbamates within the hydrophobic chiral cavities of Î³-CD showed higher diastereoselectivities in the photoproducts than those obtained in solution. The selective encapsulation of the enecarbamates and the following isomerization process are both diastereoselectively controlled by Î³-CD.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesCopper-free click chemistry for the in situ crosslinking of photodegradable star polymershttp://academiccommons.columbia.edu/catalog/ac:125398
Johnson, Jeremiah; Baskin, Jeremy M.; Bertozzi, Carolyn R.; Koberstein, Jeffrey T.; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8599Wed, 24 Mar 2010 00:00:00 +0000Bifunctional, fluorinated cyclooctynes were used for the in situ click crosslinking of azide-terminated photodegradable star polymers, yielding photodegradable polymeric model networks with well-defined structures and tunable gelation times.Chemistryjk1191, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesFRETView: a computer program to simplify the process of obtaining fluorescence resonance energy transfer parametershttp://academiccommons.columbia.edu/catalog/ac:125407
Stevens, Nathan; Dyer, Joanne; Martí, Angel A.; Solomon, Marissa Rowanda; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8602Wed, 24 Mar 2010 00:00:00 +0000The process of modeling the fluorescence resonance energy transfer (FRET) process for a donor-acceptor pair can be rather challenging, yet few computer programs exist that allow such modeling to be done with relative ease. In order to address this, we have developed a Java-based program, FRETView, which allows numerous FRET parameters to be obtained with just a few mouse clicks. Being a Java-based program, it runs equally well on all the major operating systems such as Windows, Mac OS X, Linux, Solaris. The program allows the user to effortlessly input pertinent information about the donor-acceptor pair, including the absorption and/or emission spectra, and outputs the calculated FRET parameters in table format, as well as graphical plots.Chemistryms2201, njt3Chemistry, Earth and Environmental Engineering, Chemical Engineering, Biomedical EngineeringArticlesH2, HD, and D2 inside C60: Coupled translation-rotation eigenstates of the endohedral molecules from quantum five-dimensional calculationshttp://academiccommons.columbia.edu/catalog/ac:125416
Xu, Minzhong; Sebastianelli, Francesco; Bačić, Zlatko; Lawler, Ronald; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8605Wed, 24 Mar 2010 00:00:00 +0000We have performed rigorous quantum five-dimensional (5D) calculations of the translation-rotation (T-R) energy levels and wave functions of H2, HD, and D2 inside C60. This work is an extension of our earlier investigation of the quantum T-R dynamics of H2@C60 [M. Xu et al., J. Chem. Phys. 128, 011101 (2008)] and uses the same computational methodology. Two 5D intermolecular potential energy surfaces (PESs) were employed, differing considerably in their well depths and the degree of confinement of the hydrogen molecule. Our calculations revealed pronounced sensitivity of the endohedral T-R dynamics to the differences in the interaction potentials, and to the large variations in the masses and the rotational constants of H2, HD, and D2. The T-R levels vary significantly in their energies and ordering on the two PESs, as well as from one isotopomer to another. Nevertheless, they all display the same distinctive patterns of degeneracies, which can be qualitatively understood and assigned in terms the model which combines the isotropic three-dimensional harmonic oscillator, the rigid rotor, and the coupling between the orbital and the rotational angular momenta of H2/HD/D2. The quantum number j associated with the rotation of H2, HD, and D2 was found to be a good quantum number for H2 and D2 on both PESs, while most of the T-R levels of HD exhibit strong mixing of two or more rotational basis functions with different j values.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesDynamic properties and optical phase conjugation of two-photon pumped ultrashort blue stimulated emission in a chromophore solutionhttp://academiccommons.columbia.edu/catalog/ac:125422
He, Guang S.; Qin, Hai-Yan; Zheng, Qingdong; Prasad, Paras N.; Jockusch, Steffen; Turro, Nicholas J.; Halim, Marlin; Sames, Dalibor; Ågren, Hans; He, Sailinghttp://hdl.handle.net/10022/AC:P:8607Wed, 24 Mar 2010 00:00:00 +0000The dynamic properties of two-photon pumped blue lasing (~470 nm) in the solution of an organic chromophore [2-acetyl-6-(dimethylamino)naphthalene], excited by ~160-fs laser pulses at ~775 nm, have been studied. Both the forward and backward stimulated emission are enhanced by feedback from the reflection at the two optical windows of the solution filled cuvette. Under current experimental conditions, the lasing wavelengths in the forward and backward directions were almost the same, but both blueshifted compared to the fluorescence peak wavelength of the sample solution. The temporal behavior of the lasing output was recorded by a high-speed streak camera system. The multipulse structure and spectral properties of the output lasing are semiquantitatively explained. In addition, excellent optical phase-conjugation properties of the backward stimulated emission were observed; the aberration influences from an aberrator on the backward lasing beam were automatically removed.Chemistrysj67, njt3, ds584Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesMetal Acetylacetonates as General Precursors for the Synthesis of Early Transition Metal Oxide Nanomaterialshttp://academiccommons.columbia.edu/catalog/ac:125419
Willis, Amanda; Chen, Zhuoying; He, Jiaqing; Zhu, Yimei; Turro, Nicholas J.; O'Brien, Stephenhttp://hdl.handle.net/10022/AC:P:8606Wed, 24 Mar 2010 00:00:00 +0000A versatile, convenient, and nontoxic solvothermal method for the synthesis of nanocrystalline iron, chromium, and manganese oxides is described. This method employs the reactions of metal acetylacetonate precursors and oxygen-containing solvents in a reaction to prepare metal oxide nanoparticles. Characterization of these nanocrystalline materials was carried out employing transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), and elemental analysis.Chemistrynjt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesProbing the photoreactivity of aryl chlorides with oxygenhttp://academiccommons.columbia.edu/catalog/ac:125385
Da Silva, José P.; Jockusch, Steffen; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8595Tue, 23 Mar 2010 00:00:00 +0000Molecular oxygen was used to probe the mechanism of the phototransformation of chlorobenzene and 4-chloroanisole in organic solvents. Laser flash photolysis, electron paramagnetic resonance and product distribution studies clarified the reaction mechanisms of these compounds under a wide range of conditions. The main primary photochemical reaction step is the homolytic cleavage of the C-Cl bond to produce a triplet radical pair in the solvent cage. In non-polar solvents hydrogen abstraction, after radical diffusion, leads to reduction. In polar solvents, in addition to H-abstraction, electron transfer within the caged radical pair occurs and leads to an ion pair (phenyl cation and Cl-). In the presence of oxygen, phenyl radicals can form phenylperoxyl radicals which have a bathochromically shifted absorption, thus making the homolytic cleavage visible by flash photolysis. The peroxyl radicals can couple, leading to more polar compounds, or undergo back reaction to the phenyl radical. For concentrations of the aryl chlorides of higher than 10-3 M, dimerization becomes an important transformation process and occurs after reaction of the transients with ground state molecules. In addition, excimer formation is postulated to be involved in the dimerization process.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesPhysical and chemical quenching rates and their influence on stereoselective photooxygenation of oxazolidinone-functionalized enecarbamateshttp://academiccommons.columbia.edu/catalog/ac:125388
Solomon, Marissa Rowanda; Sivaguru, J.; Adam, Waldemar; Jockusch, Steffen; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8596Tue, 23 Mar 2010 00:00:00 +0000Physical and chemical quenching rate constants were measured for the reaction of singlet oxygen with oxazolidinone-functionalized enecarbamates to investigate the role of vibrational deactivation in product stereoselectivity.Chemistryms2201, sj67, njt3Chemistry, Earth and Environmental Engineering, Chemical Engineering, Biomedical EngineeringArticlesShedding light on surfacesâ€”using photons to transform and pattern material surfaceshttp://academiccommons.columbia.edu/catalog/ac:125382
Park, Ellane J.; Carroll, Gregory T.; Turro, Nicholas J.; Koberstein, Jeffrey T. http://hdl.handle.net/10022/AC:P:8594Tue, 23 Mar 2010 00:00:00 +0000The ultimate goal of surface modification is to quantitatively control surface properties by precise manipulation of surface chemical structure at the molecular level. Advances in the understanding of molecular design principles for soft matter surfaces can be combined with the available arsenal of interesting photochemical reactions to create an exciting paradigm for surface modification: the use of photons to both transform and pattern chemical functionality at soft matter surfaces. The success of the paradigm is predicated on the ability to design and synthesize "photochemical surface delivery vehicles," complex photoactive molecules that form stable surface monolayers and subsequently deliver photoactive moieties to the surface. Shedding light onto these smart, modified surfaces brings about a wide variety of precise photochemical reactions that are preprogrammed within the surface delivery vehicle. Surface chemical patterns are formed by exposure through a mask. Some photochemical surface transformation can be considered as "green" chemistry since only photons are required as reagents. In this review, we provide a brief tutorial on photochemistry fundamentals to illustrate the nature of possible photochemical surface reactions and discuss the principles of design for photochemical surface delivery vehicles. Applications of the paradigm drawn from a variety of fields emphasize the tremendous potential for photochemical surface transformation and patterning on both hard and soft substrates.Chemistrynjt3, jk1191Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesSinglet molecular oxygen by direct excitationhttp://academiccommons.columbia.edu/catalog/ac:125391
Jockusch, Steffen; Turro, Nicholas J.; Thompson, Elizabeth K.; Gouterman, Martin; Callis, James B.; Khalil, Gamal E.http://hdl.handle.net/10022/AC:P:8597Tue, 23 Mar 2010 00:00:00 +0000Direct excitation at 1064 nm and detection of singlet molecular oxygen at 1270 nm is made possible by the availability of powerful YAG-lasers and sensitive NIR photomultipliers. Singlet oxygen was generated in condensed phase at 77 K by direct excitation at 1064 nm (without the use of sensitizers). Several luminescing species were observed by time resolved luminescence spectroscopy and luminescence lifetime measurements, including the single molecule 1Î”gand 1 Î£g+states as well as luminescence from the [1Î”g]2 simultaneous transition. As an application we propose a novel method for obtaining quantitative non-intrusive mapping of the 2-D oxygen concentrations and pressure at cryogenic temperatures, which is of importance in aircraft design for high altitudes.Chemistrysj67, njt3Chemistry, Earth and Environmental Engineering, Chemical EngineeringArticlesA covalently linked phenanthridine-ruthenium(II) complex as a RNA probehttp://academiccommons.columbia.edu/catalog/ac:125379
O'Connor, Naphtali A.; Stevens, Nathan; Samaroo, Diana; Solomon, Marissa Rowanda; Martí, Angel A.; Dyer, Joanne; Vishwasrao, Harshad; Akins, Daniel L.; Kandel, Eric R.; Turro, Nicholas J.http://hdl.handle.net/10022/AC:P:8593Tue, 23 Mar 2010 00:00:00 +0000A phenanthridine derivative covalently linked to a ruthenium complex yields an imaging probe whose fluorescence intensity and lifetime change substantially in the presence of RNA.Chemistryms2201, hv2112, erk5, njt3Biochemistry and Molecular Biophysics, Chemistry, Physiology and Cellular Biophysics, Earth and Environmental Engineering, Neuroscience, Chemical Engineering, Psychiatry, Biomedical EngineeringArticles